Abstract We tested the hypothesis that muscle microvascular O 2 pressure ( P m v O 2 ; reflecting the O 2 delivery ( Q ˙ O 2 ) to O 2 uptake ( V ˙ O 2 ) ratio) would be lowered in the spinotrapezius muscle of Goto–Kakizaki (GK) Type II diabetic rats ( n = 7) at rest and during twitch contractions when compared to control (CON; n = 5) rats. At rest, P m v O 2 was lower in GK versus CON rats (CON: 29 ± 2; GK: 18 ± 2 Torr; P < 0.05). At the onset of contractions, GK rats evidenced a faster change in P m v O 2 than CON (i.e., time constant ( τ); CON: 16 ± 4; GK: 6 ± 2 s; P < 0.05). In contrast to the monoexponential fall in P m v O 2 to the steady-state level seen in CON, GK rats exhibited a biphasic P m v O 2 response that included a blunted (or non-existent) P m v O 2 decrease followed by recovery to a steady-state P m v O 2 that was at, or slightly above, resting values. Compared with CON, this decreased P m v O 2 across the transition to a higher metabolic rate in Type II diabetes would be expected to impair blood-muscle O 2 exchange and contractile function.